Patterns and predictors of condition indices in a critically endangered fish

Hydrobiologia - Condition indices are key predictors of health and fitness in wild fish populations. Variation in body condition, therefore, can be used to identify stressful conditions that may...     

Expression of novel organic cation/carnitine transporter (OCTN2) in the mouse pancreas

Among the organic cation transporters, OCTN2 is identified as the most important carnitine transporter owing to the ability to transport carnitine. Although the OCTN2 is previously found in various tissues, there have been no reports showing the OCTN2 in the pancreas. In this study, we examined the expression and localization of OCTN2 in the mouse pancreas by the aid of an in situ hybridization technique and immunohistochemistry with anti-OCTN2 antibody. As a result, the OCTN2 expression was found in the A-cells for the first time. OCTN2 was not expressed in B-cells, notwithstanding that the metabolism of long-chain fatty acids, which are transported into the mitochondria with the help of carnitine, was expected for fatty acid-stimulated insulin secretion. Thus, this study suggests the possibility of carnitine uptake in the pancreatic A-cells through OCTN2 and implies the presence of carnitine transporter(s) other than OCTN2 in the B-cell.     

Dynamic changes in expression of heme oxygenases in mouse heart and liver during hypoxia

Heme oxygenase cleaves heme to form biliverdin, carbon monoxide (CO), and iron, and consists of two structurally related isozymes, HO-1 and HO-2. HO-2 is also known as a potential oxygen sensor. Here we show that the relative CO content in arterial blood, which reflects the total amount of endogenous heme degradation, dynamically changes in mice during acclimatization to normobaric hypoxia (10% O2), with the two peaks at 1 day and 21 days of hypoxia. The expression levels of HO-1 and HO-2 proteins were decreased by 20% and 40%, respectively, in the mouse liver at 7 days of hypoxia, which returned to the basal levels at 14 days. On the other hand, HO-1 and HO-2 proteins were increased 2-fold and 1.3-fold, respectively, in the heart at 28 days of hypoxia. Thus, hypoxia induces or represses the expression of HO-1 and HO-2 in vivo, depending on cellular microenvironments.     

Mannan-binding protein blocks the activation of metalloproteases meprin alpha and beta

Mannan-binding protein (MBP) is a C-type serum lectin that is known to be a host defense factor involved in innate immunity, and recognizes mannose, fucose, and N-acetylglucosamine residues. Although some exogenous MBP ligands have been reported, little is known about its endogenous ligands. In the present study, we found that endogenous MBP ligands are highly expressed in the brush border epithelial cells of kidney-proximal tubules by immunohistochemistry, and both meprin alpha and beta (meprins), as novel endogenous MBP ligands, have been identified through affinity chromatography and mass spectrometry. Meprins are membrane-bound and secreted zinc metalloproteases extensively glycosylated and highly expressed in kidney and small intestinal epithelial cells, leukocytes, and certain cancer cells. Meprins are capable of cleaving growth factors, extracellular matrix proteins, and biologically active peptides. Deglycosylation experiments indicated that the MBP ligands on meprins are high mannose- or complex-type N-glycans. The interaction of MBP with meprins resulted in significant decreases in the proteolytic activity and matrix-degrading ability of meprins. Our results suggest that core N-linked oligosaccharides on meprins are associated with the optimal enzymatic activity and that MBP is an important regulator for modulation of the localized meprin proteolytic activity via N-glycan binding. Because meprins are known to be some of the major matrix-degrading metalloproteases in the kidney and intestine, MBP, which functions as a natural and effective inhibitor of meprins, may contribute, as a potential therapeutic target, to tumor progression by facilitating the migration, intravasation, and metastasis of carcinoma cells, and to acute renal failure and inflammatory bowel diseases.     

Differential gene expression profiling between wild-type and ALAS2-null erythroblasts: identification of novel heme-regulated genes

To identify erythroid-specific heme-regulated genes, we performed differential expression analysis between wild-type and heme-deficient erythroblasts, which had been prepared from wild-type and erythroid-specific delta-aminolevulinate synthase-null mouse ES cells, respectively. Among 8737 clones on cDNA array, 40 cDNA clones, including 34 unknown ESTs, were first selected by their high expression profiles in wild-type erythroblasts, and evaluated further for their erythroid-lineage specificity, expression in hematopoietic tissues in vivo, and heme-dependent expression, which yielded 11, 4, and 4 genes, respectively. Because of the selection strategy employed, the final 4 were considered as the newly identified erythroid-specific heme-regulated genes. These 4 genes were uncoupling protein 2, nucleolar spindle-associated protein, cellular nucleic acid-binding protein, and a novel acetyltransferase-like protein. These findings thus suggest that heme may regulate a wide variety of hitherto unrecognized genes, and further analysis of these genes may clarify their role in erythroid cell differentiation.     

Protective mechanism of reduced water against alloxan-induced pancreatic β-cell damage: Scavenging effect against reactive oxygen species

Reactive oxygen species (ROS) cause irreversible damage to biological macromolecules, resulting in many diseases. Reduced water (RW) such as hydrogen-rich electrolyzed reduced water and natural reduced waters like Hita Tenryosui water in Japan and Nordenau water in Germany that are known to improve various diseases, could protect a hamster pancreatic β cell line, HIT-T15 from alloxan-induced cell damage. Alloxan, a diabetogenic compound, is used to induce type 1 diabetes mellitus in animals. Its diabetogenic effect is exerted via the production of ROS. Alloxan-treated HIT-T15 cells exhibited lowered viability, increased intracellular ROS levels, elevated cytosolic free Ca²⁺ concentration, DNA fragmentation, decreased intracellular ATP levels and lowering of glucose-stimulated release of insulin. RW completely prevented the generation of alloxan-induced ROS, increase of cytosolic Ca²⁺ concentration, decrease of intracellular ATP level, and lowering of glucose-stimulated insulin release, and strongly blocked DNA fragmentation, partially suppressing the lowering of viability of alloxan-treated cells. Intracellular ATP levels and glucose-stimulated insulin secretion were increased by RW to 2–3.5 times and 2–4 times, respectively, suggesting that RW enhances the glucose-sensitivity and glucose response of β-cells. The protective activity of RW was stable at 4 °C for over a month, but was lost by autoclaving. These results suggest that RW protects pancreatic β-cells from alloxan-induced cell damage by preventing alloxan-derived ROS generation. RW may be useful in preventing alloxan-induced type 1-diabetes mellitus. This revised version was published online in August 2006 with corrections to the Cover Date.     

Functional involvement of Tudor and dPRMT5 in the piRNA processing pathway in Drosophila germlines

In Drosophila, the PIWI proteins, Aubergine (Aub), AGO3, and Piwi are expressed in germlines and function in silencing transposons by associating with PIWI‐interacting RNAs (piRNAs). Recent studies show that PIWI proteins contain symmetric dimethyl‐arginines (sDMAs) and that dPRMT5/Capsuleen/DART5 is the modifying enzyme. Here, we show that Tudor (Tud), one of Tud domain‐containing proteins, associates with Aub and AGO3, specifically through their sDMA modifications and that these three proteins form heteromeric complexes. piRNA precursor‐like molecules are detected in these complexes. The expression levels of Aub and AGO3, along with their degree of sDMA modification, were not changed by tud mutations. However, the population of transposon‐derived piRNAs associated with Aub and AGO3 was altered by tud mutations, whereas the total amounts of small RNAs on Aub and AGO3 was increased. Loss of dprmt5 did not change the stability of Aub, but impaired its association with Tud and lowered piRNA association with Aub. Thus, in germline cells, piRNAs are quality‐controlled by dPRMT5 that modifies PIWI proteins, in tight association with Tud.     

Dual wavelength imaging allows analysis of membrane fusion of influenza virus inside cells

Influenza virus hemagglutinin (HA) is a determinant of virus infectivity. Therefore, it is important to determine whether HA of a new influenza virus, which can potentially cause pandemics, is functional against human cells. The novel imaging technique reported here allows rapid analysis of HA function by visualizing viral fusion inside cells. This imaging was designed to detect fusion changing the spectrum of the fluorescence-labeled virus. Using this imaging, we detected the fusion between a virus and a very small endosome that could not be detected previously, indicating that the imaging allows highly sensitive detection of viral fusion.